At present, the micro optical image stabilization voice coil motor technology has been widely applied to high-end mobile phones, and can effectively reduce the probability of blurred images during photographing in a low-light environment, and reduce the disturbing jitter in the image. However, compared with ordinary autofocus motors, optical image stabilization voice coil motors have a complex design and low production yield and efficiency, and require high costs. Therefore, this technology has not been widely applied to middle-end and low-end mobile phones, and most mobile phone users have not enjoyed the benefits of this technology.
Currently, micro optical image stabilization voice coil motors may be classified into the following three types, with their names and principles being as follows:
1. camera-module-axis-shifting-type: the voice coil motor controls the lens and the image sensor to rotate together.
2. lens-translation-type: the voice coil motor controls the lens to translate, with the image sensor being kept still.
3. lens-axis-shifting-type: the voice coil motor controls the lens to rotate, with the image sensor being kept still.
The above three types of motors have their respective advantages, but the lens-axis-shifting-type motor has the simplest structure.
The structure of a typical lens-axis-shifting-type optical image stabilization voice coil motor includes a housing, a base, at least one group of elastic material, at least three groups of magnets, at least three independent coils, and a lens carrier. The housing and the base form a fixed structure. The elastic material connects a movable structure including the lens carrier to the fixed structure to form a spring oscillator system having multiple degrees of freedom, so that the lens can rotate in two directions (for the purpose of optical image stabilization), and displace along the optical axis (for the purpose of auto-focusing). The coils and the magnets may be located respectively in the fixed and movable structures, or respectively in the movable and fixed structures.
Lens-axis-shifting-type optical image stabilization voice coil motors may be classified into three types according to the compositions of the lens carrier and the elastic material.
The first type of lens-axis-shifting-type optical image stabilization voice coil motor includes at least two groups of conductive elastic materials. The conductive elastic materials of this type of motor needs to be elastic and conductive (for example, made of a metal), and can allow a current to flow through during normal operation (for example, conduct electricity to the coils). The two groups of conductive elastic materials connects the upper and lower parts of the lens carrier to the fixed structure. Because such a structure needs to mechanically connect the lens carrier and the conductive elastic materials located above and below the carrier (for example, using an adhesive), and electrically connect the coils on the lens carrier and two groups of springs (for example, using a solder), the production difficulty is increased. In addition, because the two ends of the coil is respectively connected to the upper conductive elastic material which is used as a common end and the lower conductive elastic material which is used as a current input end, the entire loop circuit is long, and easily causes electromagnetic interference to nearby elements (especially the image sensor). Moreover, because the axis-shifting-type motor needs to allow for easy axis-shifting rotation, the spring coefficient of the upper group of conductive elastic material needs to be lower than that of the lower group of elastic material, resulting in low resistance to dropping, and reducing the reliability of this type of motor in the drop test.
The second type of lens-axis-shifting-type optical image stabilization voice coil motor only includes one group of conductive elastic material to connect the lens carrier and the fixed structure. The lens carrier may include three coils. One of the coils controls the lens to move along the optical axis to achieve auto-focusing, and the other two coils control the lens to rotate in two directions for axis shifting, to achieve optical image stabilization. However, the average position of the focusing coil and the average position of the axis-shifting coil are distant from the average position of the magnet. When the motor stroke changes, the density of the magnetic field passing through the coil is likely to change nonlinearly, leading to nonlinearity of the properties of the motor. To achieve an ideal focusing and image stabilization effect, the type of motor requires a complex control and adjustment system, leading to an increase in the costs of the entire image stabilization system and adjustment system.
The third type of lens-axis-shifting-type optical image stabilization voice coil motor does not include a conductive elastic material, and includes only one or two elastic materials, to connect the movable structure including the lens carrier and the magnets. Because the movable structure of this type of motor does not require electrical connection, this type of motor is more suitable for mass production than the first and second types of motors. In addition, the average positions of the focusing and axis-shifting coil of the first and third types of motors can be very close to the average position of the magnet, the nonlinearity problem of the second type of motor can be avoided. However, the magnets of the third type of motor, which are located in the movable structure, may experience interference from an approaching external strong magnetic field.